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A heater core is a radiator-like device used in heating the cabin of a
vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), wa ...
. Hot
coolant A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosi ...
from the vehicle's
engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...
is passed through a winding tube of the core, a heat exchanger between coolant and cabin air. Fins attached to the core tubes serve to increase surface area for heat transfer to air that is forced past them by a fan, thereby heating the passenger compartment.


How it works

The
internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
in most cars and
truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construction ...
s is cooled by a water and antifreeze mixture that is circulated through the engine and radiator by a
water pump A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...
to enable the radiator to give off engine heat to the atmosphere. Some of that coolant can be diverted through the heater core to give some engine heat to the cabin, or adjust the temperature of the conditioned air. A heater core is a small radiator located under the
dashboard For business applications, see Dashboard (business). A dashboard (also called dash, instrument panel (IP), or fascia) is a control panel set within the central console of a vehicle or small aircraft. Usually located directly ahead of the drive ...
of the vehicle, and it consists of conductive
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
or
brass Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other wit ...
tubing with cooling fins to increase surface area. Hot coolant passing through the heater core gives off heat before returning to the engine cooling circuit. The squirrel cage fan of the vehicle's ventilation system forces air through the heater core to transfer heat from the coolant to the cabin air, which is directed into the vehicle through vents at various points.


Control

Once the engine has warmed up, the coolant is kept at a more or less constant temperature by the thermostat. The temperature of the air entering the vehicle's interior can be controlled by using a valve limiting the amount of coolant that goes through the heater core. Another method is blocking off the heater core with a door, directing part (or all) of the incoming air around the heater core completely, so it does not get heated (or re-heated if the
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
compressor is active). Some cars use a combination of these systems. Simpler systems allow the driver to control the valve or door directly (usually by means of a rotary knob, or a lever). More complicated systems use a combination of electromechanical actuators and
thermistor A thermistor is a type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word thermistor is a portmanteau of ''thermal'' and ''resistor''. Thermistors are divided based on their conduction ...
s to control the valve or doors to deliver air at a precise temperature value selected by the user. Cars with dual climate function (allowing driver and passenger to each set a different temperature) may use a heater core split in two, where different amounts of coolant flow through the heater core on either side to obtain the desired heating.


Air conditioning

In a car equipped with
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
, outside air, or cabin air if the recirculation flap has been set to close the external air passages, is first forced, often after being filtered by a cabin air filter, through the air conditioner's evaporator coil. This can be thought of as a heater core filled with very cold liquid that is undergoing a phase change to gas (the evaporation), a process which cools rather than heats the incoming air. In order to obtain the desired temperature incoming air may first be cooled by the air conditioning and then heated again by the heater core. In a vehicle fitted with manual controls for the heater and air conditioning compressor, using both systems together will dehumidify the air in the cabin, as the evaporator coil removes moisture from the air due to condensation. This can result in increased air comfort levels inside the vehicle. Automatic temperature control systems can take the best course of action in regulating the compressor operation, amount of reheating and blower speed depending upon the external air temperature, the internal one and the cabin air temperature value or a rapid defrost effect requested by the user.


Engine cooling function

Because the heater core cools the heated coolant from the engine by transferring its heat to the cabin air, it can also act as an auxiliary radiator for the engine. If the radiator is working improperly, the operator may turn the heat on (together with the cabin blower fan placed on full speed, and with the windows opened) in the passenger cabin, resulting in a certain cooling effect on the overheated engine coolant. This idea only works to a certain degree, as the heater core is not large enough nor does it have enough cold air going through it to cool large amounts of coolant significantly.


Possible problems

The heater core is made up of small piping that has numerous bends. Clogging of the piping may occur if the coolant system is not flushed or if the coolant is not changed regularly. If clogging occurs the heater core will not work properly. If coolant flow is restricted, heating capacity will be reduced or even lost altogether if the heater core becomes blocked. Control valves may also clog or get stuck. Where a blend door is used instead of a control valve as a method of controlling the air's heating amount, the door itself or its control mechanism can become stuck due to
thermal expansion Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of the average molecular kinetic ...
. If the climate control unit is automatic, actuators can also fail. Another possible problem is a leak in one of the connections to the heater core. This may first be noticeable by smell (
ethylene glycol Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...
is widely used as coolant and has a sweet smell); it may also cause (somewhat greasy) fogging of the
windshield The windshield (North American English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from the elements. ...
above the windshield heater vent. Glycol may also leak directly into the car, causing wet upholstery or carpeting.
Electrolysis In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...
can cause excessive corrosion leading to the heater core rupturing. Coolant will spray directly into the passenger compartment followed with white coloured smoke, a significant driving hazard. Because the heater core is usually located under the dashboard inside of the vehicle and is enclosed in the ventilation system's ducting, servicing it often requires disassembling a large part of the dashboard, which can be labour-intensive and therefore expensive. Since the heater core relies on the coolant's heat to warm the cabin air up, it will not begin working until the engine's coolant warms up enough. This problem can be resolved by equipping the vehicle with an auxiliary heating system, which can either use electricity or burn the vehicle's fuel in order to rapidly bring the engine's coolant to operating temperatures.


Air cooled engines

Engines that do not have a water cooling system cannot heat the cabin via a heater core; one alternative is to guide air around the (very hot) engine exhaust manifold and then into the vehicle's interior. Temperature control is achieved by mixing with unheated outside air. Air-cooled
Volkswagen Volkswagen (),English: , . abbreviated as VW (), is a German Automotive industry, motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a ...
engines use this method. Another example is the air-cooled
Briggs & Stratton Vanguard The Briggs & Stratton Vanguard Big Block V-Twin is a series of American piston engines, designed and produced by Briggs & Stratton of Wauwatosa, Wisconsin for use in commercial applications. They have also been adapted for use as ultralight airc ...
, used in the ultra and microlight flight amateur construction scene. This method for cockpit heating is a simple option for the
Spacek SD-1 Minisport The Spacek SD-1 Minisport is a Czech amateur-built aircraft, designed by Igor Špaček and produced by Spacek sro of Hodonin. The aircraft was also produced for a short time in the United States by SkyCraft Airplanes of Orem, Utah as a li ...
and other homebuilt sportplanes. However, depending on the design, this can cause a safety issue where a leak in the exhaust system will begin to fill the passenger cabin with deadly fumes.


Reuse for other purposes

Car heat cores are also used for Do-It-Yourself projects, such as for cooling homemade liquid cooling systems for computers.Reuse of heater cores for PC liquid cooling system
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See also

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Air cooling Air cooling is a method of dissipating heat. It works by expanding the surface area or increasing the flow of air over the object to be cooled, or both. An example of the former is to add cooling fins to the surface of the object, either by maki ...
*
Internal combustion engine cooling Internal combustion engine cooling uses either air or liquid to remove the waste heat from an internal combustion engine. For small or special purpose engines, cooling using air from the atmosphere makes for a lightweight and relatively simple sys ...
*
Radiator (engine cooling) Radiators are heat exchangers used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine. In ...
*
Radiator (heating) Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating. Denison Olmsted of New Haven, Connecticut, appears to have been the earliest person to use the term ...
*
Water cooling Cooling tower and water discharge of a nuclear power plant Water cooling is a method of heat removal from components and industrial equipment. Evaporative cooling using water is often more efficient than air cooling. Water is inexpensive and non ...


References


External links

{{Wiktionary, heater core
entire cooling system
Automotive technologies Cooling technology Engine cooling systems Heating, ventilation, and air conditioning Heat exchangers